The DNA of canine adenovirus (canAV 1, strain Behring H.c.c. 269) was characterized in detail. The molecular weight of canAV DNA was (20.1 +/- 0.1) x 10(6) daltons as determined by contour length measurements, and 19.9 x 10(6) daltons as determined by restriction enzyme analysis. A terminal protein was found to be covalently linked to the 5' ends of canAV DNA. Physical maps of viral DNA were constructed for BamHI, ClaI, SacI, SalI, and SmaI enzymes. Three international strains of canAV [American Type Culture Collection (ATCC) catalogue No. VR-800, VR-293, and VR-133] were analyzed under the same conditions. CanAV 1 (ATCC VR-133 and VR-293) had DNA cleavage patterns identical to the H.c.c. 269 strain, whereas the DNA cleavage pattern of canAV 2 (ATCC VR-800) was clearly different.